Epigenetic Gene Regulation by JAK1 Kinase in Diffuse Large B-Cell Lymphoma

描述(申请人提供)：弥漫性大B细胞淋巴瘤(DLBCL)是最常见的非霍奇金淋巴瘤，最具侵袭性的亚型，活化的B细胞样(ABC)，在三年内导致60%的患者死亡。ABC DLBCL的一个重要特征是通过细胞因子IL6和IL10自分泌信号，而IL6和IL10是癌症生长所必需的。细胞因子信号通路的分子机制仍未明确，将是本研究的重点。在初步结果中，我们确定了细胞因子途径下游的结构性激活的激酶为JAK1。癌细胞需要JAK1活性才能存活；通过RNA干扰或药物抑制剂AZD1480抑制JAK1对培养的ABC DLBCL细胞是致命的。作为一种酪氨酸激酶，JAK1通过磷酸化STAT3以及通过一种令人惊讶的非规范机制来调节基因的表达，直接针对组蛋白H3进行酪氨酸41磷酸化(H3Y41p)。这一修饰的全基因组图谱确定了2582个JAK1靶基因。其中一些通过H3Y41p诱导表达的基因不依赖于STAT3，包括癌基因MYC和重要的NF-kB基因MYD88和IRF4。鉴于核因子-kB的激活是ABC DLBCL的标志，并导致细胞因子IL-6或IL-10的自身分泌，JAK1和核因子-kB信号通路形成一个正反馈回路，促进癌细胞的存活和增殖。这些发现支持JAK1通过两条互补的途径调节基因表达以促进癌细胞存活和增殖的假设，JAK1下游靶基因是ABC DLBCL治疗干预的潜在候选基因。事实上，IRF4上游的Bruton酪氨酸激酶(BTK)抑制剂Ibrutinib对ABC DLBCL有效。然而，由于耐药性，伊布鲁替尼只能实现暂时缓解。这项拟议的研究将检验这样一种假设，即通过联合靶向治疗克服对伊布鲁替尼的获得性耐药性有助于进一步改善ABC DLBCL的结果。具体地说，在ABC DLBCL异种移植小鼠模型和原始患者样本中，将通过其抑制剂双重阻断NF-kB和JAK1。这项研究的目标是建立一个概念框架，以了解JAK1是如何通过这两种不同的(STAT3介导或染色质靶向)机制来介导转录激活的，识别JAK1的新分子靶点，并开发一种新的疾病治疗策略。

DESCRIPTION (provided by applicant): Diffuse large B-cell lymphoma (DLBCL) is the most common form of non-Hodgkin lymphoma, and the most aggressive subtype, activated B-cell-like (ABC), kills 60% of patients within three years. One important feature of ABC DLBCL is autocrine signaling by the cytokines IL6 and IL10, which is essential for cancer growth. The molecular mechanisms underlying the cytokine signaling pathway remain undefined and will be a focus of this study. In preliminary results, we identified the constitutively activated kinase downstream of the cytokine pathway as JAK1. Cancer cells require JAK1 activity for survival; JAK1 inhibition by RNA interference or the pharmaceutical inhibitor AZD1480 is lethal to cultured ABC DLBCL cells. As a tyrosine kinase, JAK1 regulates gene expression through phosphorylating STAT3 as well as through a surprising non- canonical mechanism, directly targeting the histone protein H3 for tyrosine 41 phosphorylation (H3Y41p). Genome-wide mapping of this modification identified 2,582 JAK1 target genes. Some of these genes that are induced for expression through H3Y41p are independent of STAT3, including the oncogene MYC and important NF-kB genes MYD88 and IRF4. Given that NF-kB activation is a hallmark of ABC DLBCL and causes auto-secretion of the cytokines IL6 or IL10, JAK1 and NF-kB signaling pathways form a positive feedback loop to promote the survival and proliferation of cancer cells. These findings support the hypothesis that JAK1 regulates gene expression via two complementary pathways to promote cancer cell survival and proliferation, and JAK1 downstream target genes are potential candidates for therapeutic intervention in ABC DLBCL. In fact, the Bruton tyrosine kinase (BTK, upstream of IRF4) inhibitor, Ibrutinib, has been effective in ABC DLBCL. Due to drug resistance, however, Ibrutinib only achieves a temporary remission. The proposed research will test the hypothesis that overcoming acquired resistance to Ibrutinib by combined targeted therapies helps further improve outcomes of ABC DLBCL. Specifically, dual interruption of NF-kB and JAK1 by their inhibitors will be conducted in ABC DLBCL xenograft mouse models as well as in primary patient samples. The goals of the proposed research are to establish a conceptual framework for understanding how JAK1 mediates transcription activation through these two distinct (STAT3-mediated or chromatin targeting) mechanisms, to identify novel molecular targets of JAK1, and to develop a new therapeutic strategy for the disease.